Protective cover having sensor holder part, bearing device including the protective cover, and method for manufacturing the protective cover having the sensor holder part

A method for manufacturing, by use of an injection mold die, a protective cover having a cup shape for use in a bearing device, the bearing device including:

• a bearing including, on an outer peripheral surface thereof, an inner ring having an inner ring raceway surface, an outer ring having, on an inner peripheral surface thereof, an outer ring raceway surface, and a rolling element rolling between the inner ring raceway surface and the outer ring raceway surface;
• a magnetic encoder including N poles and S poles, which are alternately arranged at regular intervals in a circumferential direction, the magnetic encoder being located at an inward-side end portion of the bearing and fixed to the inner ring;
• and
• a magnetic sensor being opposed to magnetic poles of the magnetic encoder, for detecting rotation of the magnetic encoder,
• the protective cover being configured to be mounted to the outer ring so as to seal the inward-side end portion of the bearing,
• the protective cover including:
• a disc part made of a synthetic resin;
• a sensor holder part made of the synthetic resin and protruding inward from the disc part;
• and
• a protruding part made of the synthetic resin, protruding inward from the disc part to be continuous with the sensor holder part,
• the disc part having a separation wall which is thinner than other portions of the disc part and separates the magnetic encoder and the magnetic sensor from each other,
• the injection mold die being configured to mold the protective cover and including:
• a gate located at an inward-side face of the protruding part;
• and
• a columnar part protruding toward the gate to provide a thickness reduction part extending inward so as to be close to the gate, at an outward-side face of the protruding part,
• the method comprising:
• closing the injection mold die, injecting a molten synthetic resin material from the gate into a cavity of the die, and solidifying the material to perform injection molding;
• and
• opening the injection mold die and taking out a solidified molded article.